BRPI0806740A2 - water purification composition, water purification process and use of water purification composition - Google Patents

Abstract

WATER PURIFICATION COMPOSITION, WATER PURIFICATION PROCESS AND USE OF WATER PURIFICATION COMPOSITION. It is a water purifying composition. The invention relates particularly to a water purifying composition which is especially useful for removing traces of harmful contaminants such as arsenic, as well as removing microorganisms such as viruses, bacteria and cyst to make water suitable for use. human consumption. Accordingly, an object of the present invention is to provide a composition for water purification that meets the arsenic removal requirements. In particular, another object of the present invention is to provide a water purification composition that provides low arsenic purified water that meets WHO standards of less than 10 ppb, especially arsenic compounds (III ). Accordingly, the present invention provides a water purification composition comprising: (a) a coagulant which is a water soluble inorganic metal salt having a trivalent cation; (b) a flocculating agent which is a high molecular weight water soluble polymer; (c) an adsorbent which is a water insoluble titanium, zirconium, iron, copper or zinc oxide, hydroxide or oxohydrox; and (d) a biocide which is a halogen compound.

Description

Patent Invention Descriptive Report

WATER PURIFICATION COMPOSITION, WATER PURIFICATION PROCESS AND USE OF WATER PURIFICATION COMPOSITION

Field of the Invention

The invention relates to a composition for water purification. The invention relates particularly to a water purifying composition which is especially useful for removing traces of harmful contaminants such as arsenic, as well as removing microorganisms such as viruses, bacteria and cyst to make water suitable for consumption. human.

Background of the Invention

A large portion of the world's population lives in developing and underdeveloped countries, where there is a severe lack of clean drinking water. A high percentage of these people live in rural areas where there are no water purification systems. Many people have to rely directly on ground and / or underground water sources such as wells, tubular wells, lakes and rivers. Often these water sources are contaminated with sewage, and industrial and agricultural discharges.

The various types of water purification systems available such as those using UV radiation, halogenated resins, reverse osmosis, etc., are not very convenient for use in rural areas as they require running water and / or electricity or are not economical to use. consumer. In this regard, many people in rural areas resort to boiling water to kill pathogenic microorganisms by eliminating them from their drinking water. This is often not feasible either, as boiling requires a large amount of fuel that is becoming increasingly scarce. Still, there are many areas in the world that are naturally contaminated with high amounts of inorganic impurities such as arsenic. Arsenic is an extremely harmful contaminant. People continue to ingest water with these high levels of microorganisms and impurities such as arsenic, which are responsible for the high mortality and morbidity in these areas.

Arsenic is one of the most toxic contaminants found in the environment. Arsenic is found in soils, rocks, natural waters and organisms. Arsenic is the twentieth most abundant element in the earth's crust. The most common states of arsenic oxidation are +3 and +5. Of all arsenic compounds present in the environment, of particular interest is arsenite (which is arsenic in the form As (III)), which is 25 to 50 times more toxic than arsenate (which is arsenic in the form As (V)) and 70 times more toxic than the methylated species dimethylsinate (DMA) and monomethylsonate (MMA). These facts indicate why it would be of prime interest to develop technologies for the removal of As (III) from drinking water.

Inorganic arsenic is identified as a group I carcinogen for humans. More than 100 million people worldwide are affected by arsenic-contaminated drinking water. Drinking water in many of these areas has an arsenic content as high as 300 parts per billion (ppb). WHO and USEPA (US Environmental Protection Agency) recommend arsenic maximum contaminant limit (MCL) in potable water of 10 ppb. Available technologies for arsenic removal include membrane separation, ion exchange and adsorption. These technologies require expensive equipment that is not accessible in many parts of the world or unsuccessful in removing arsenic, especially As (III) arsenic in the WHO recommended specification. Still, boiling water, which many people turn to for water purification, does not remove arsenic. Thus, one of the biggest challenges in this field is the weak removal of arsenic (III). In addition, while arsenic in purified water must meet these severe demands, technology must also ensure the removal of harmful microorganisms such as cysts, bacteria and viruses to a level that is safe for people to consume. According to EPA, water of any unknown origin can be made microbiologically safe to drink if removal of bacteria Iog 6, virus Iog 4 and cyst Iog 3 are obtained. Thus, generally accepted removal criteria for bacteria, viruses and cysts include removal of yog 6, yog 4 and yog 3.

Numerous chemical methods of water purification are known and used at municipal, neighborhood and residential levels. Chemicals include coagulants and flocculants to precipitate suspended and dissolved impurities and biocides to kill microorganisms.

Document W002 / 00557 (Procter and Gamble) describes a water purification composition together with a nutrient additive, not to mention purification and clarification of drinking water, where the need has been found in many parts of the world to improve nutrition and health standards. The composition described comprises essentially a primary coagulant, a binding flocculant and a binding aid. Although this document calls for the removal of arsenic, the present inventors have noted the need for improvement in technology to meet stringent WHO drinking water standards.

Titanium dioxide was used to remove arsenic from water. Stevens Institute of Technology document US6919029 (2005) teaches the specific use of titanium dioxide for improved arsenic removal. The present inventors have found that the mere use of titanium dioxide alone does not provide almost complete removal of arsenic.

JP2005058987 relates to pour water purification compositions containing nine components, namely: calcium sulfate, aluminum sulfate, silica, soda, polymeric flocculant, talc, zeolite, activated carbon and titanium oxide. This patent application describes the detoxification of sludge dump water using titanium oxide as a photocatalyst. The present inventors have found that this composition is not suitable for raw water purification to meet the drinking water criteria set by WHO and other health agencies.

The present inventors worked diligently to solve this problem. They found that the use of adsorbents such as titanium dioxide in a flocculation formulation, while providing improved removal of arsenic (V) compounds from water, is not able to meet the requirements for removal of arsenic (III) compounds, the most toxic and most difficult to remove from arsenic compounds. They then worked on other fronts to solve this problem and found that the use of certain selective biocides solves the problem of removing all arsenic compounds to meet strict WHO standards. In addition, selective biocides ensure sufficient removal of microorganisms.

Thus, an object of the present invention is to provide a water purification composition which solves most of the problems encountered when using the compositions reported in the past. Another object of the invention is a water purification composition that provides low arsenic water that meets WHO standards of less than 10 ppb, especially arsenic (III) compounds. Still another object of the present invention is to provide a water purification composition that also meets the high standards of microbiological removal of Yog 6 from bacteria, Yog 4 from viruses and Yog 3 from cysts.

Summary of the Invention

According to one aspect of the present invention, there is provided a water purifying composition comprising:

(a) a coagulant which is a water-soluble inorganic metal salt having trivalent cation;

(b) a flocculating agent which is a high molecular weight water soluble polymer;

(c) an adsorbent which is a water insoluble titanium, zirconium, iron, copper or zinc oxide, hydroxide or oxohydroxides; and

(d) a biocide which is a halogen compound.

It is particularly preferred that the adsorbent is titanium dioxide or iron oxohydroxide.

According to a preferred aspect of the invention there is provided a water purifying composition comprising two parts which are spatially separated, wherein the first part comprises the biocide and the second part comprises the flocculant and coagulant.

Detailed Description of the Invention

All parts herein are by weight unless otherwise specified.

The water purification composition of the present invention comprises a coagulant, a flocculant, a selective adsorbent and a selective biocide.

The coagulant is a compound which is a water-soluble inorganic metal salt having trivalent cation. Suitable trivalent cations are Al3 + and Fe3 +. The coagulant is generally carbon free. Examples of coagulant agents are ferric sulfate, aluminum sulfate and aluminum polychloride. Without wishing to be bound by theory, it is believed that these coagulants when added to water form gelatinous hydroxide compounds at pH greater than or equal to 6. The coagulation mechanism via gelatinous hydroxy formation is optimal when the pH is adjusted to pH. between 6 and 8.5. The gelatinous precipitate carries fine suspended particles and microbes as it precipitates or coagulates. The coagulant is preferably present in the range of 5 to 50%, more preferably 15 to 40% by weight of the composition.

The flocculating agent according to this invention is a high molecular weight water soluble polymer compound. Examples of flocculating agents are polysaccharides (dextran, cellulose), proteins, modified celluloses (hydroxyethyl / hydroxypropyl or carboxymethyl) and polyacrylamides, preferably high molecular weight polyacrylamides. It is especially preferred that the polacrylamide is either anionic or nonionically modified, more preferably anionically modified. Suitable molecular weights of these polyacrylamides are in the range 105 to 107. The preferred flocculating agent is Superfloc (from Cytec). Preferred amounts of the flocculating agent are from 0.5 to 15%, more preferably from 1 to 10%, and more preferably from 2 to 8% by weight of the composition.

The water purification composition of the invention comprises an adsorbent solely selected to impart the desired properties.

The adsorbent is a water insoluble titanium, zirconium, iron, copper or zinc oxide, hydroxide or oxohydroxide. Especially preferred adsorbents are water insoluble titanium and oxide hydroxide or hydroxide. Suitable adsorbents are titanium dioxide, zirconium oxide, iron oxide, copper oxide, zinc oxide, iron oxohydroxides, titanium oxohydroxides, zirconium oxohydroxides or combinations of these adsorbents. The most preferred adsorbents are titanium dioxide, titanium oxohydroxide, iron oxide, iron hydroxide or iron oxohydroxide, where titanium dioxide and iron oxohydroxide are most preferred. Preferred amounts of adsorbent are in the range of 5 to 70%, more preferably 10 to 50%, and most preferably 15 to 30% by weight of the composition.

The composition of the invention comprises a biocide which is a halogen compound. More preferred halogen compounds are those of chlorine or iodine, more preferably those of chlorine. Suitable chlorine compounds are inorganic compounds such as sodium hypochlorite, calcium hypochlorites, chlorine dioxide, or chloramines, or chlorine compounds such as sodium dichloroisocyanurates, or trichloroisocyanuric acid. The biocide is preferably present in an amount ranging from 1 to 20%, more preferably from about 2 to 12% by weight of the composition. The most preferred biocide is calcium hypochlorite. The present inventors have found that not all biocides are effective in meeting the objectives of the present invention. Several conventional biocides such as quaternary ammonium compounds, triazine, glutaraldehyde, isothiazoline, organic titanium compounds, carbamates, methylene thiocyanate have been used and although useful for microbiological removal they have shown little efficacy in satisfying arsenic removal. Thus, the invention is especially suited for the removal of arsenic, especially when water is heavily contaminated with arsenic compounds which are in the form of As (III) 1 which has always been difficult to achieve using prior art methods.

The water purifying composition works best when it is packaged to have a moisture content of no more than 5%, more preferably no more than 3%, and more preferably no more than 2% by weight of the composition.

The purifying action of the composition of the invention may be obtained at the pH of available raw water. As a preferred aspect, the pH of the composition may be adjusted to the desired range by including a buffering agent in the composition. Suitable buffering agents include calcium oxide, sodium carbonate or sodium bicarbonate. The buffering agent when present is included in an amount ranging from 0.5 to 10% by weight of the composition.

The water purification composition may optionally comprise a co-sorbent. The sorbent is preferably a material that is capable of adsorbing high levels of water and organic or inorganic compounds. A suitable coadsorbent is clay. Examples of clay include montmorillonite clay (diocteadral smectite clay), laponite, hectorite, nontronite, saponite, volkonsite, sauconite, beldelite, alevarlita, ilite, haloisite, attapulgite, mordenite, kaolin, and bentonite. A highly preferred clay according to this invention is bentonite clay. When included, co-sorbents are present in an amount ranging from 5 to 75%, more preferably from about 10 to 60% by weight of the composition.

According to a preferred aspect of the invention, the water purification composition is distributed as a two component system. The two component system comprises a first part and a second part which are kept spatially separated. The first part comprises the biocide and the second part comprises the flocculant and coagulant. In another aspect, the adsorbent is present in the second part of the two component system. When distributed as a two-component system, it is preferred that the first part comprises less than 5% moisture by weight of said first part. In the two-component system, the sorbent, if present, may be included in both the first and second parts or may be present in either part.

Another preferred aspect of the invention is to provide the second part with a biocide quencher that is capable of reacting with the biocide to make it safe and aesthetically acceptable for human consumption. Suitable suppressors are sodium thiosulfate and ascorbic acid. The suppressor is preferably in an amount ranging from 1 to 20% by weight of the second part, more preferably from about 2 to 12% by weight of the second part.

The solid form is the most suitable form of the composition of the invention. Suitable solid forms include powder, granule and tablet forms, where the powder form is most preferred. When distributed as a two-component system, the most preferred form is the powder form in both the first and second parts.

The water purification composition of the invention is preferably distributed in amounts ranging from 0.5 to 10 g, more preferably from 1 to 5 g. These are usually added to 5 to 20 liters of water. When delivered as a two-component system, the appropriate weight of the first part is 0.01 to 5 g, more preferably 0.1 to 1 g and the appropriate weight of the second part is 0.5 to 10 g.

The water purification composition of the invention may be distributed to the consumer in any suitable packaging form. When formed as tablets, the package may be a metallized laminate or blister package. When formed as powders, the suitable packaging is a metallized laminate. However, the foil packaging must be such that halogenated compounds which usually react with metals are kept separate from the metal portion of the laminate by the use of suitable polymeric layers in the metal layer.

According to another aspect of the invention, there is provided a process for purifying water comprising the steps of (i) mixing the composition of the invention with the water to be purified and (ii) separating the flocculated mass from the mixture.

When the product is configured as a two-part system, a suitable process comprises the sequential steps of mixing the composition of the first part with the water to be purified; followed by the step of mixing the composition of the second part and then separating the flocculated mass from the mixture. The first part is usually mixed for a period of 0.5 to 5 minutes and the water is then allowed to stand for a period of 2 to 10 minutes, after which the second part is then added. The mixture is then mixed for a period of 0.5 to 5 minutes and left to stand for 2 to 10 minutes again. The flocculated mass is then allowed to settle and then separated from the mixture usually by filtration or decantation. A simple cloth can be used for filtration.

The process of the invention is especially suitable for purifying arsenic-containing water. In contaminated areas, the average arsenic concentration in raw water is about 300 ppb by weight. Using the process of the invention, it is possible to obtain purified water having an arsenic content as low as less than 10 ppb by weight of the purified water.

The invention will now be illustrated by the following non-limiting examples.

Examples

Preparation of test water: 10 liters of reverse osmosis purified water were taken and 15 g of sea salt, 0.025 g humic acid and 1.5 g of fine dust (Arizona test dust) were added. Total dissolved salts were less than 50 ppm. Arsenic compounds, either sodium arsenate (Na2HAs04.7H20) in which arsenic is in the form of As (V) or sodium arsenite (NaAsO2) in which arsenic is as As (II) were added to the test water, as desired.

Arsenic content determination

Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) (Varian-Vista-PRO) was used to measure the total arsenic concentration (> 50 ppb) in the solution. Total arsenic concentrations less than 50 ppb were analyzed by inductive plasma coupled mass spectrometry (ICP-MS) (Eldrin 9000). In both analytical methods, samples were injected into the equipment without any preconcentration or predilution and total arsenic concentrations were measured.

Comparative Example - A

A test water containing 300 ppm arsenic from sodium arsenate (arsenic form (V)) was used. The purification process was as follows:

Purification Process: 10 liters of test water was placed in a bucket and the composition as shown in Table-1 was added to the test water and stirred for one minute after which the water was allowed to stand for five minutes. The flocculated mass was then filtered through a layered cloth. The arsenic content of the purified water was measured and the result is summarized in Table-1.

Comparative Example - B

A test water containing 300 ppb of arsenic from sodium arsenite (Arsenic (III) form) was used. The purification process was as used for Comparative Example - A. The arsenic content of the purified water was measured and the result is summarized in Table-1.

Example 1

A water purification composition as shown in Table-1 was used for water purification. The composition was a two component system, with the first component having calcium hypochlorite and the second component having aluminum polychloride, polyacrylamide and titanium dioxide. The purification process was as follows.

Purification Process: 10 liters of test water was placed in a bucket and the composition as shown in Table-1 was added to the test water and stirred for one minute, and then the water was allowed to stand for five minutes. Thereafter, the second component was added and stirred for one minute and then rested for five minutes. The flocculated mass was then filtered through a layered cloth. The arsenic content of the purified water was measured and the result is summarized in Table 1.

Example 2

A composition according to Example-1 was used. The test water was similar to that used in Example-1 except that the test water contained 150 ppb sodium arsenite and 150 ppb sodium arsenate which are generally found in arsenic contaminated soil water. The arsenic content of the purified water was measured and the result summarized in Table 1.

Example 3

A water purification composition similar to that of Example-1 was used as shown in Table-1 except that iron oxide was used in place of titanium dioxide. The composition was prepared as a two component system.

Table 1

<table> table see original document page 12 </column> </row> <table>

The data in Table 1 indicate that by using the prior art composition (Comparative Example - A) As (V) removal standards can be obtained, but the purification standard for As (III) ( Comparative Example - B). However, by using the compositions according to the present invention (Examples 1 to 3), it is possible to ensure the removal of Arsenic as As (III) alone or as a mixture of As (III) and As (V) forms. .

Biocidal Effectiveness

A test water as used for Example-1 was prepared and microorganisms, i.e. cyst, bacteria and viruses, as shown in Table-2 were added thereto. The test water was purified according to the procedure used for Example-1. The amount of microorganisms in the purified water was determined and the result is summarized in Table-2. The method used to measure the amount of various microorganisms in water is described in detail in the publication "Tropical Medicine and International Health, Volume 11, pp. 1399-1405, September 2006, in the article entitled" Microbiological performance of a water. treatment unit designed for household use in developing countries ", by Thomas Clasen1 Suresh Nadakatti and Shashikala Menon.

Table 2

<table> table see original document page 13 </column> </row> <table>

The data indicate that the composition according to the invention is capable of purifying water containing harmful microorganisms to a high degree of purification required to maintain the good health of those who consume water, namely the composition ensures at least removal. log 6 bacteria, virus Yog 4 removal and cyst Yog 3 removal.

Various prior art compositions (Comparative Examples CaF) and compositions outside the scope of the invention (Comparative Example G) were tested as shown in Table-3. Test water was as used for Example-1.

Comparative Example - C

The water purification composition as shown in Table-3 was prepared as a one component system and the process according to Comparative Example - A was used to purify the test water.

Comparative Example - D

The composition was prepared as shown in Table-3 as a two component system. The test water was purified according to the procedure used in Example 1.

Comparative Example - E

A composition was prepared as shown in Table-3 as a one component system and a process according to Comparative Example - A was used.

Comparative Example - F

A composition as shown in Table 3 was prepared as a one component system. The test water was purified according to the process used in Comparative Example - A.

Comparative Example - G

The composition was prepared as shown in Table 3 as a two component system. The test water was purified according to the procedure used in Example 1.

The results of the experiments (Comparative Examples C to G) in terms of arsenic content in purified water are summarized in Table 3.

Table 3

<table> table see original document page 14 </column> </row> <table>

CaHypo: Calcium Hypochlorite

CPB: Cetyl Pyridinium Bromide The data in Table 3 indicate that compositions described in the prior art (Comparative Examples C to F) are not able to meet the arsenic removal criteria. Moreover, the use of a conventional biocide (Comparative Example G) alone is not able to meet the arsenic removal criteria.

Comparative examples - H to K

Experiments were performed using compositions as shown in Table 4, where various popular absorbents were used. The process used was similar to that used in Example 1. The result of the arsenic content in the purified water is shown in Table 4. The results of Example 1 are also shown for comparison.

Table 4

<table> table see original document page 15 </column> </row> <table>

The data in Table 4 indicate that only the use of a selective adsorbent in the composition of the invention provides the synergistic benefit of arsenic removal while the use of conventional adsorbents does not provide this benefit.

Claims (27)

WATER PURIFICATION COMPOSITION, WATER PURIFICATION PROCESS AND USE OF WATER PURIFICATION COMPOSITION 1. A water purifying composition, characterized in that it comprises: (a) a coagulant which is a water-soluble inorganic metal salt having a trivalent cation; (b) a flocculating agent which is a high molecular weight water soluble polymer; (c) an adsorbent which is a water insoluble titanium, zirconium, iron, copper or zinc oxide, hydroxide or oxohydroxides; and (d) a biocide which is a halogen compound. Water purification composition according to claim -1, characterized in that the halogen is chlorine or iodine. Water purification composition according to claim -1 or 2, characterized in that the halogen compound is calcium hypochlorite. Water purification composition according to any one of claims 1 to 3, characterized in that the biocide is present in an amount ranging from 1 to 20% by weight of the composition. Water purification composition according to any one of claims 1 to 4, characterized in that the adsorbent is titanium dioxide or titanium oxohydroxide. Water purification composition according to any one of claims 1 to 5, characterized in that the adsorbent is present in an amount in the range of 5 to 70% by weight of the composition. Water purification composition according to any one of claims 1 to 6, characterized in that the coagulant is polyaluminium chloride, aluminum sulfate or ferric sulfate. Water purification composition according to any one of claims 1 to 7, characterized in that the coagulant is present in an amount in the range of 5 to 50% by weight of the composition. Water purification composition according to any one of claims 1 to 8, characterized in that the flocculating agent is anionically modified polyacrylamide. Water purification composition according to any one of claims 1 to 9, characterized in that the flocculating agent is present in an amount in the range of 0.5% to 15% by weight of the composition. Water purification composition according to any one of claims 1 to 10, characterized in that it comprises a co-adsorbent which is capable of adsorbing high levels of water and organic or inorganic compounds. Water purification composition according to claim 11, characterized in that the co-sorbent is bentonite clay. Water purification composition according to claim 11 or 12, characterized in that the co-sorbent is present in an amount ranging from 5 to 75% by weight of the composition. Water purification composition according to any one of claims 1 to 13, characterized in that it comprises a buffering agent capable of maintaining the pH in the range of 6 to 8.5 when the composition is dissolved / dispersed in water. Water. Water purification composition according to claim 14, characterized in that the buffering agent is selected from calcium oxide, sodium carbonate or sodium bicarbonate. Water purification composition according to claim 14 or 15, characterized in that the buffering agent is present in an amount ranging from 1 to 10% by weight of the composition. Water purification composition according to any one of claims 1 to 16, characterized in that it comprises two parts which are spatially separated, wherein the first part comprises the biocide and the second part comprises the flocculant and the coagulant agent. Water purification composition according to claim 17, characterized in that the second part comprises said adsorbent. Water purification composition according to claim 17 or 18, characterized in that said first part comprises less than 5% moisture by weight of said first part. Water purification composition according to any one of claims 17 to 19, characterized in that the second part comprises a biocide suppressor which is capable of reacting with the biocide to make it safe for human consumption. Water purification composition according to claim 20, characterized in that said suppressor is sodium thiosulfate or ascorbic acid. 22. Water purification process, characterized in that it comprises the steps of: i. mixing the composition as claimed in any one of claims 1 to 16 with the water to be purified, and ii. separate the flocculated mass from the mixture. 23. Water purification process, characterized in that it comprises the steps of: i. mixing the composition of the first part as defined in any one of claims 17 to 21 with the water to be purified; ii. mixing the composition of said second part as defined in any one of claims 17 to 21; and iii. separate the flocculated mass from the mixture. Use of a composition as defined in any one of claims 1 to 21, characterized in that it is in the reduction of drinking water arsenic to a level of less than 10 ppb in purified water. Use of a composition as defined in any one of claims 1 to 21, characterized in that it is in the reduction of drinking water bacteria, wherein log 6 removal of bacteria is obtained. Use of a composition as defined in any one of claims 1 to 21, characterized in that it is in the reduction of drinking water viruses, wherein a log 4 removal of viruses is obtained. Use of a composition as defined in any one of claims 1 to 21, characterized in that it is in the reduction of drinking water cysts, wherein a log 5 removal of cysts is obtained.